Implement oidc

[Jeidnx]

see https://github.com/TeamPiped/Piped/issues/2571

[Jeidnx]

I have cleaned up the code and made sure everything works. Here are a few things worth mentioning:

• This only supports providers which have the openid connect discovery standard (.well-known/openid-configuration) implemented, which should be all relevant providers.
• User deletion currently only works if the provider supports the optional max_age parameter and properly returns the auth_time claim. We could drop this restriction, but that would allow one-click deletion of accounts without verifying the identity of the user.
• This also only works with providers which support the PKCE code authorization flow, which again should be most of them.

Please let me know if there are any questions or concerns. I have tested this and from my view this could be merged

edit: Found the alternative for TokenRequest..